1. Technical Field
This invention generally relates to toner supply mechanisms for laser printers and copiers. More particularly, this invention relates to a lockout device for a toner hopper which prevents an operator from over-filling a toner hopper.
2. Background Art
The increase in the number of abilities and features of laser printers has resulted in tremendously complex electronic and mechanical designs. With more complex designs come more potential problems and more possibilities for operator error. For instance, with the advent of color copying and color laser printing, it is possible for the operator to use the wrong color of toner to refill one of the toner hoppers, and unless the manufacturer anticipates this and provides some type of safe guard mechanism to prevent it, this can have disastrous consequences. Depending upon the sophistication of the operator, or more importantly how broad of a market a particular product is targeted for, the number of safe guard devices necessary to insure reliable operation is almost directly proportional to the number of features the product has.
Typical of this phenomenon is the set of electrical and mechanical checks or interlocks built into the toner supply system of the KONICA color laser printer engine. The KONICA color laser engine has as its first check level, a piezoelectric toner level sensor which serves to notify the operator that a particular toner hopper is running low on toner and needs to be refilled. Second, the toner cartridges and hopper lids are keyed to prevent the operator from inserting the wrong color of toner into the wrong hopper. Third, the hopper cover is interlocked so that it cannot be opened unless a toner cartridge is inserted and once it is opened, the toner cartridge cannot be removed until the cover is closed. Finally, once the toner hopper is closed, both the toner hopper and the toner cartridge are resealed so the toner cartridge can be removed.
Unfortunately, even with all of the checks that are provided, it is still possible for the operator to make a serious mistake when refilling the printer with toner. Nothing prevents the operator from trying to fill a full or partially full toner hopper. This mistake is especially likely on a color laser printer. For instance, an operator seeing the magenta toner empty light on the display panel might not pay attention to the particular color, might simply grab the wrong color, or may even assume that because the magenta toner is empty, so too must be the black, cyan and yellow hoppers. In any event, the toner in the cartridge cannot completely empty into the hopper so the hopper cover cannot be shut and the cartridge cannot be removed. As a result, the mixing paddle inside the hopper can become jammed which will in turn result in the toner hopper gear drive failing when the printer is operated. In any case, a service call is required to fix the device.